Timing imbalance in the meiosis of the F₁ hybrid Oryza sativa × O. australiensis

Abstract

The meiosis in the F₁ hybrid Oryza saliva × O. australiensis was studied. Contrary to the observations of Gopalakrishnan (1959), true allosyndetic bivalents were not found at metaphase I. The most frequent associations were non-chiasmatic, end-to-end pseudobivalents. Autosyndetic bivalents were recorded mostly in the complement belonging to O. sativa, which are distinguishable by their smallness and lighter staining. The meiotic cycle exhibits timing imbalance with earlier condensation, and possibly migration, of the univalents belonging to O. australiensis. The data on meiotic pairing in the F₁ hybrid and the comparative morphology of O. sativa, O. officinalis and O. australiensis inicate that the last species is the most primitive member, having originated from the pre-Sativa and pre-Officinalis complex.